62 THE POCKET ANATOMY 



Posterior spinal : arises opposite posterior part of medulla, 

 passes down back of cord behind roots of nerves, anasto- 

 mising with spinal branches coming through intervertebral 

 foramina. 



Anterior spinal : given off near end of artery, descends in 

 front of medulla, unites with opposite fellow just below fora- 

 men magnum to form a single artery, which is continued 

 along the cord, anastomosing like the posterior artery ; sup- 

 plies pia mater and cord. 



Posterior inferior cerebellar : arising near pons, passes 

 backwards and outwards between roots of hypoglossal and 

 then between spinal accessory and pneumogastric nerves, to 

 reach under surface of cerebellum ; divides into two branches, 

 one continuing backwards in sulcus between two hemispheres, 

 the other outwards to supply under surface of cerebellum ; 

 anas, superior cerebellar. Supplies hemisphere, vermiform 

 process, and choroid plexus of 4th ventricle. 



Bulbar arteries enter medulla. 



THYROID AXIS : a short thick trunk from front of artery near 

 scalenus anticus, quickly dividing into : 



Inferior thyroid : passes upwards on vertebral artery and 

 under internal jugular vein ; then inwards and downwards 

 behind sheath of carotid and sympathetic (middle cervical 

 ganglion), finally outwards and upwards to under part of thy- 

 roid body ; anas, opposite fellow and superior thyroid. 



Branches : 



Ascending cervical: arises as inferior thyroid turns behind 

 carotid sheath, ascends parallel to phrenic nerve and between 

 scalenus anticus and rectus anticus major, supplying them, 

 the cord and its membranes. 



Inferior laryngeal : upwards on trachea to back of larynx, 

 with recurrent laryngeal nerve. 



Tracheal : to trachea ; anas, bronchial. 



CEsophageal : to supply resophagus. 



Thyroid : to gland. 



Muscular. 



Supra- scapular : runs downwards at first, over scalenus 

 anticus and phrenic nerve, crosses 3rd part of subclavian, 

 then runs transversely outwards, behind and parallel to 

 clavicle, to upper edge of scapula under cover of trapezius ; 

 inclining downwards with nerve to pass over transverse liga- 

 ment on supra-scapular notch, enters supra-spinous fossa in 

 contact with the bone beneath supra-spinatus, which it sup- 

 plies. It then winds over neck of scapula to infra-spinous 

 fossa ; anas, with posterior scapular and dorsalis scapulae. 



